1. Field of the Invention
The invention relates to signature panels commonly found on plastics substrates such as identification and financial cards, methods for forming such signature panels and methods for mounting signature panels on substrates.
2. Discussion of Related Art
Most identification and transaction cards currently issued carry a signature panel for the holder of the card to inscribe his signature. In the case of financial cards such as credit cards, these cards are mass produced in batches and passed to a bureau service which is responsible for imprinting the name and account number of the holder by embossing as well as recording the information on the magnetic stripe. All of the cards then become unique. At this stage they do not possess any biological attributes but when the card is received the holder is required to apply a signature on the signature strip. This signature is commonly the only characteristic of the card which ties the card in biometric terms to the holder.
Clearly the signature panel must be securely affixed to the card to deter fraudulent substitution and it is common for there to be printing on the surface of the panel which will be irreversibly changed if an attempt is made to alter a signature.
In early times signature panels were applied to cards by the screen printing of a suitably pigmented formulation. These panels had relatively low security against fraudulent alteration because of the absence of security printing on their surface.
In 1970 Addressograph-Multigraph, in US-A-3545380, described plastic cards, such as credit cards, having a signature receptive strip with a non-reproducible pattern formed on the surface of the signature strip. Methods of applying such a strip by making a transfer foil which allows the transfer of the printed signature accepting panel under conditions of heat and pressure are also disclosed.
The printing applied to the surface of the signature accepting panel comprises fine linework which the patent states is intended to be difficult to reproduce. The transferrable panels are prepared by printing such linework on the carrier which may be polyethylene terephthalate.
Commercially, cards with such signature panel markings are produced by printing with flexographic inks, that is inks which are set by evaporation. Such cards continue to be available today. The panels however have minimal security.
The level of security protection of such printed panels while enhanced above bare panels is limited. There was a need to provide signature accepting panels of enhanced security. The industry thus developed paper signature panels. Paper panels were able to accommodate enhanced levels of security printing because the substrate was paper rather than a plastic coating. While offering high levels of security the panels are however slow to apply to cards. Lengths of paper strips having repeated security markings are generally laid across large sheets of plastic which are printed with multiples of the card images. These strips would be adhered into place often in a hot laminating press. The large sheets are then cut into individual card blanks.
This is a slow process. Care has to be taken to ensure that the strips are properly bonded to the cards to avoid the possibility of delamination by criminals. The bonding occurs during the card manufacturing process rather than at the end when the card blanks are ready (with any rejects removed).
In 1985 EP-A-149542 addressed the question of security rainbow printing on the surface of credit cards. In passing there was mention as to signature panels incorporating solvent sensitive and/or erasable inks. The patent also mentions the use of rainbow printing on the signature panel in the form of a microprinting design. This again used paper signature panels.
These paper strips have high integral strengths and are well finished. They are usually made chemically reactive against the typical forger's solvents and bleaches.
Although paper strips are advantageous in that they enable a variety of special security printing effects to be achieved by using offset methods including multiple colour printing, their use is labour intensive and their cost is high. They are also more prone to delamination than hot stamped signature strips.